BIOL240 Study Guide - Quiz Guide: Pyrimidine Dimer, Facultative Anaerobic Organism, Anaerobic Organism
3 Feb 2016
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Document Summary
Except temperature, the hydrogen ion concentration (ph) of an organism"s environment exerts the greatest influence on its growth. Ph limits the activity of enzymes with which an organism is able to synthesize new protoplasm. There exists for each organism an optimum concentration of hydrogen ions where it grows best. The ph values above and below which an organism fails to grow are respectively referred to as the maximum and minimum hydrogen ion concentrations. These values hold only when other environmental factors remain constant (= if the composition of the medium, incubation temp, or osmotic pressure is varied, the hydrogen ion requirements become different) Obligate aerobes: bacteria cannot exist w/o oxygen. Obligate anaerobes: cannot grow in the presence of oxygen. Facultative anaerobes: grow in either the presence or absence of oxygen, but show much better growth when oxygen is available to them. Microaerophiles: require oxygen, but only in limited amounts.
